Removal of monocyclic aromatic hydrocarbons from gases



Patented Aug. 11, 1931 UNITED STATES PATENT OFFICE MATHIAS PIER, OF HEIDELBERG, WALTER BOESLER, OF LUDWIGSHAFEN-ON-THE- RHINE, AND AUGUST .EISENHUT, OF HEIDELIBERG, GERMANY, ASSIGNOBS TO I. G. FARBENINDUSTRIE AKTIENGESELLSCHAFT, OF FRANKFORT-ON-THE-MAIN, GER- MANY, A CORPORATION OF GERMANY REMOVAL OF MONOOYCLIC ABOMATIC HYDROCABBONS FROM GASES No Drawing. Application filed August 13, 1926, Serial No. 129,097, and. in Germany September 1, 1925.

Benzene and its homologues such as toluene, xylene and the like which all are hereinafter for brevity referred to as mono-cyclic aromatic hydrocarbons, are

generally removed from gases containing them for example from coke oven gases, by washing with suitable tar oils.

We have now found that the normally liquid products obtained by the treatment of distillable carbonaceous materials of the nature of coal in all its varieties, tars, mineral oils, and distillation products thereof with hydrogen or gases containing or giving rise to hydrogen at elevated temperatures and preferably under elevated pressure (which treatment may be called a destructive hydrogenation and is disclosed in the Australian patent of Krauch, No. 1217 of March 29, 1926), or fractions of such products are very efiicient washing agents for the removal of mono-cyclic aromatic hydrocarbons from gases. With the said hydrogenation products mono-cyclic aromatic hydrocarbons are removed from gases more completely and rapidly and the quantities of washing agent may be smaller than with the tar oils hitherto in use for the said purpose. For example a product obtained by destructive hydrogenation of brown coal producer tar under a pressure of 200 atmospheres and at about 150" C. in the presence.

of a catalyst containing molybdenum, zinc and copper shows much better absorbing action than the usually employed tar oil. Further, with the washing agents according to the present invention a formation of resinous bodies occurs only to a considerably smaller extent than with tar oils, so that the new washing agents can be used for the said purpose much longer than the washing agents hitherto employed.

The following example will further illustrate how our present invention may be carried out in practice and what the advantages thereof are, but the invention is not limited to this example.

In a tower filled with so-called Raschig rings, a gas containing mono-cyclic aromatic hydrocarbons is washed with a product of the destructive hydrogenation of brown coal producer tar. Another part of the same gas is washed in the same manner with a coal tar oil boiling between about 200 and 300 C. which is substantially free from naphthalene. The quantity of mono-cyclic aromatic hydrocarbons absorbed by the hydrogenation product is about 20 per cent greater than that absorbed from the same quantity of gas by the tar oil. The washing oils are then subjected to steam distillation. In the case of tar oil the distillate consists chiefly ofcom onents of the tar oil and con tains ample quantities of phenols, while in the case of the hydrogenation product the distillate contains about 95 per cent of mono-cyclic aromatic hydrocarbons, but no phenols.

Similar results are obtained with hydrogenation products of other carbonaceous materials.

We claim:

1. The process of removing a monocyclic aromatic hydrocarbon from a gas containing the same which comprises washing the gas with a normally liquid fraction from the destructive hydrogenation of a distillable carbonaceous material selected from the class consisting of coal, tars, mineral oils and the distillation products thereof, said fraction having a substantially lower volatility than the monocyclic aromatic hydrocarbon to be removed.

2. The process of removing a monocyclic aromatic hydrocarbon from a gas containing the same, which comprises washing the gas with a normally liquid fraction from the destructive hydrogenation of brown coal producer tar obtained under a pressure of about 200 atmospheres and a temperature of about 450 C. in the presence of a catalyst comprising molybdenum, said fraction having a substantially lower volatility than the monocyclic aromatic hydrocarbon to be removed.

In testimony whereof we have hereunto set our hands.

MATI-IIAS PIER. WALTER BOESLER. AUGUST EISENHUT. 

